Receiver sheets for electrostatic recording

ABSTRACT

A receiver sheet for electrostatic recording comprises a dense paper base sheet having a bulk porosity of less than 200 Sheffield units as measured by a Sheffield Porosimeter with a 1 1/2 inch orifice and air at 1 1/2 psi; a thin first conductive coat on one side of the paper base containing 20 to 30 percent by weight of conductive material, distributed so as to provide the conductive material in a coat weight of 0.05 to 0.25 pound per 1000 sq/ft. of paper; a dielectric coat on top of the first conductive coat, having a surface resistivity greater than 1 X 1016 ohms per square at 20% relative humidity; and a second conductive coat on the opposite side of the paper base. A preferred conductive coat comprises a vinylbenzyl quaternary ammonium compound mixed with a starch derivative binder and coating clay. Both the first conductive coat and the dielectric coat can be applied from aqueous dispersion or solution without adversely affecting resistivity of the dielectric coat.

United States Patent Funderburk Jan. 21, 1975 [75] Inventor: Kit Funderburk, Rochester, N.Y.

[73] Assignee: Eastman Kodak Company,

Rochester, N.Y.

[22] Filed: Mar. 16, 1973 [21] Appl. N0.: 342,011

[52] US Cl 117/218, 117/226, 117/227, 117/71 R, 117/76 P, 117/153, 96/15, 162/138, 346/135 [51] Int. Cl G03g 5/02 [58] Field of Search ..117/76 P, 71 R, 217, 218, 117/226, 153, 227; 162/135, 137, 138; 96/15; 346/135 [56] References Cited UNITED STATES PATENTS 3,652,268 3/1972 Rowe 117/218 3,652,271 3/1972 Bornath et a1v 117/218 3,672,930 6/1972 Trachtenberg 117/37 LE 3,672,988 6/1972 Tamai et a1 117/218 3,707,402 12/1972 Yamaguchi et al. 346/135 3,709,728 1/1973 Anderson 3,759,744 9/1973 Schliesman 117/218 3,783,021 1/1974 York 117/218 Primary ExaminerMichael Sofocleous Attorney, Agent, or Firm-11. M. Chapin [57] ABSTRACT A receiver sheet for electrostatic recording comprises a dense paper base sheet having a bulk porosity of less than 200 Sheffield units as measured by a Sheffield Porosimeter with a 1 V2 inch orifice and air at 1 & psi; a thin first conductive coat on one side of the paper base containing 20 to 30 percent by weight of conduc' tive material, distributed so as to provide the conductive material in a coat weight of 0.05 to 0.25 pound per 1000 sq/ft. of paper; a dielectric coat on top of the first conductive coat, having a surface resistivity greater than 1 X 10 ohms per square at 20% relative humidity; and a second conductive coat on the opposite side of the paper base. A preferred conductive coat comprises a vinylbenzyl quaternary ammonium compound mixed with a starch derivative binder and coating clay. Both the first conductive coat and the dielectric coat can be applied from aqueous dispersion or solution without adversely affecting resistivity of the dielectric coat.

9 Claims, No Drawings RECEIVER SHEETS FOR ELECTROSTATIC RECORDING BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel coated paper, to novel paper base receiver sheets for electrostatic recording, and to a novel method for manufacturing such paper and paper base receiver sheets.

2. The Prior Art The principles of electrostatic recording are well known, having been described in many patents and publications. In one system for electrostatic recording, a paper base carrying an electrically conductive coating and a photoeonductive coating has the image reproduced directly thereon.

In another system an electrostatic charge pattern is first produced on a photoeonductive element, and is then transferred to an electrographic receiver sheet which generally comprises a paper base having coatings of both electrically conductive material and electrically insulating dielectric material thereon. The transferred latent image is then developed by contacting the charge pattern with a liquid or dry toner. Alternatively, prior to transfer, toner can be applied to the photoeonductive element and then transferred to the receiver sheet by contacting the two surfaces and applying an electrical potential between them. In either case the image can then be fixed by heat, pressure, solvent vapor or the like. Exemplary patents describing systems of the prior art include such patents as US. Pat. Nos. 2,825,814; 3,011,918; 3,110,621; 3,493,427 and 3,519,819.

The receiver sheets of the prior art have had certain deficiencies which are overcome by the present invention. For example, in some of the prior art it has been necessary to apply a precoat layer on top of the paper base to prevent a subsequently applied conductive coat from penetrating into the paper basefWithout such a precoat, excessive amounts of expensive conductive material have been required to compensate for this undesirable migration into the paper stock. This is particularly true when employing conventional size-press coating techniques because a large amount of paper penetration is inherent with this method on conventional porous paper bases. Such a precoat has been required also to prevent fibers from the paper base from entering the dielectric coat and supplying a path by which charge can leak off, in papers in which a conductive coat is not placed under the dielectric coat.

Another disadvantage of the prior art is that satisfactory receiver sheets could not be manufactured by coating the conductive material and the dielectric material both from aqueous solutions or dispersions. In the past, when a conductive coating comprising a water soluble conductive material was applied from an aqueous solution or dispersion, followed by an aqueous solution or dispersion of dielectric material on top of the conductive coat, it was found that conductive material migrates from the conductive coat into the dielectric coat and reduces, or even destroys, the dielectric nature of the dielectric coat so that the receiver sheet becomes practically useless for electrography. A solution to this problem has been desired because coating from aqueous solutions or dispersions would have the advantages over organic solvent coating of reducing cost for solvent, avoiding the need for solvent recovery systems, and avoiding air and water pollution.

SUMMARY OF THE INVENTION In accordance with my invention the disadvantages of the prior art are overcome by a combination of features such that the cost and efficiency of paper base re ceiver sheets are greatly improved. As a first feature of my invention, this is accomplished by providing a high density paper base which is characterized by a bulk porosity of less than 200 Sheffield units, and preferably or less Sheffield units, as measured by a Sheffield porosimeter with a We inch orifice and air at 1V2 pounds per square inch pressure. This high density paper base is not readily penetrable by the materials ordinarily used to form conductive coatings. Consequently, substantially none of a subsequently applied conductive coating penetrates the high density paper support, so that a much thinner coat and much lower concentration of conductive material in the conductive coating are required than previously, with consequent reduction in cost. Moreover, a precoat is not necessary on the dense paper base before applying the conductive coating.

As a second important feature, this dense paper makes it possible to apply an extremely thin electrically conductive coat from an aqueous solution or dispersion while maintaining adequate conductivity. The conductive coat is so thinly distributed on the paper base that the conductive material of the coat is present in a coat weight between only about 0.05 and about 0.25 pound per 1,000 square feet of paper for electrographic receiver sheets; or between 0.001 and 0.5 when the coated paper is to be used otherwise, as described hereinafter. This can be done by size-press coating techniques which normally would cause penetration into a paper base. Such a conductive coating remains water dissolvable after drying (by dissolvable is meant disintegratable, whether or not by solution in water).

As a third important feature, the final coat of dielectric material can also be applied from an aqueous solution or disperson on top of the previously applied water dissolvable conductive coating and yet, surprisingly, v

there is practically no migration of the water soluble conductive material from the conductive coating into the aqueous dielectric coating which remains substantially free of conductive material so that the electrical charge acceptance of the dielectric coat remains extremely high, for example about 375 volts as opposed to only about 50 volts for the prior art wherein conductive material has migrated into the dielectric coating.

As a fourth important feature, pollution of air and water by organic solvents is eliminated by applying all coatings from aqueous systems.

The success of my novel receiver sheets is believed to be due to a combination of the particular high density paper stock of my invention with the extremely thin conductive coating, and the extremely small quantity of electrically conductive material therein, which preclude any significant migration of electrically conductive material into the dielectric coating to adversely affect the resistivity of the latter.

The novel electrographic receiver sheets described above are prepared by providing a dense paper base.

sheet having the low Sheffield porosity defined above, applying on one side of the paper base a first aqueous dispersion or solution containing, on a dry basis. be-

tween about 20 and 30 percent by weight (advantageously about 28 percent) of electrically conductive material, 50 to 60 percent (desirably about 58 percent) of clay or other solid pigment, and to 25 percent (desirably about 14 percent) of starch or other binder, as a coating so thin that the conductive material is distributed in a coat weight between about 0.05 and 0.25 pound per 1000 square feet of paper, and then causing the water to evaporate from the first aqueous dispersion or solution, leaving a dry water dissolvable first conductive coat. Coating can be done by size-press technique, brushing, blade coating, air knife, transfer roll, spraying, or any other suitable coating method.

There is then applied on top of the dry first conductive coat, a second aqueous solution or dispersion comprising dielectric material, and water is caused to evaporate from the second aqueous solution or dispersion, leaving a dry dielectric coat having a surface resistivity greater than I X 10 ohms per square at 20 percent relative humidity with parallel bar electrodes at 500 volts.

The water can be evaporated in any desired way, as by impinging hot air jets against the coated paper, passing the paper over heated drums, passing the paper through a zone where it is heated by infra red lamps or by microwave heaters, or passing it through a heated oven.

Specific formulations of the special high density paper base, of the conductive coat, and of the dielectric coat will be described in detail hereinafter.

Normally the opposite or back side of the paper base also carries a conductive coat which may or may not have the same formulation as the thin conductive coat described above.

For example, it may comprise conductive salts or conductive carbons dispersed in a suitable binder; or it may be a vacuum deposited metal such as silver, nickel, or aluminium; or it may be an unformulated conductive resin such as Dow ECR-34 (trademark) or such as conductive resin as a carboxy ester lactone of the type described in U.S. Pat. No. 3,007,901. Also, an interlayer can be used between the paper base and the conductive coating on its back side.

The'sheets described above, but without the dielectric coat, can be used directly as antistat paper for the manufacture of photographic products or other materials requiring an antistatic paper support, or they can be coated with photoconductive material such as zinc oxide coatings, or coatings containing organic photoconductors for use in electrophotography. For such uses (other than receiver sheets) a wider range of conductor distribution is permissible such as 0.001 to 0.5 pound of conductor per 1000 square feet of paper base.

THE SPECIFIC EMBODIMENTS Example 1 A raw paper base sheet of about 13 pounds per 1000 square feet basis weight is formed from a cellulosic pulp comprising water and a blend comprising 60 percent hardwood kraft fiber and 40 percent softwood bleached sulfide fiber, containing the following additives, percentages being by weight based on the fiber:

0.5 percent carboxymethyl cellulose 0.75 percent Kymene 557 (trademark of Hercules Incorporated) wet strength additive (a cationic amino epichlorohydrin resin)* 0.5 percent Aquapel 360x (trademark of Hercules Incorporated) (an alkyl ketene dimer paper sizing agent) 12 percent Titanox AMO (trademark of Titanium Pigments Division of National Lead Co.) load (anatase titanium dioxide) 0.4 percent Accostrength (trademark of American Cyanamid Co.) retention aid (an anionic acrylamide resin)* 1.5 percent DuPont SPK optical brightener 19.5 g/3500 pounds of fiber of Sandoz Blue MP dye (Sandoz Chemical Co.)

*tlescrihcd in US. Pat. No. 3.592.731

The aqueous pulp is subjected to an unusually high level of mechanical refining with both a double disk refiner at kw and a jordan refiner at 80-86 kw, in series, with stock consistency of about 3.5 percent, to produce highly fibrillated fibers. The final Williams slowness value of the pulp is to seconds, whereas pulps usually are only refined to 30 to 50 seconds. The pulp is formed into paper by conventional manufacturing steps (without calendering) to produce a final dry paper having a Sheffield porosity value of 120 Sheffield units with a 1% inch orifice at 1 /2 pounds per square inch air pressure, which corresponds to about 73 seconds air resistance (TAPPI Standard T- 460-M-49).

This base paper is then size-press coated on one side, nip application technique, with an aqueous dispersion containing 40 percent total solids, balance water, to form a thin conductive coating thereon. The solid ingredients of the formulation are as follows, in parts by weight:

100 parts Hydrasperse (trademark of J. M. Huber Corp.) No. 2 coating clay (a predispersed water washed Georgia kaolin clay) 0.1 part tetrasodium pyrophosphate 25 parts Essex gum 1390 (trademark of Penick and Ford Ltd.) (an ether derivative of potato starch) 50 parts Dow ECR-34 conducting agent (a polyvinylbenzyltrimethylammonium chloride available from Dow Chemical Co.)

After drying, the resulting conductive coat is about 2 microns thick, contains conductive polymer in a distribution of only 0.12 pound per 1000 square feet of paper, and has a surface electrical resistance of 9.12 X 10 ohms per square at about 20 percent relative humidity as measured with parallel bar electrodes at 500 volts.

A dielectric coat is then applied on top of the conductive coat from an aqueous dispersion containing 20 total solids, balance water (and no photoconductor), and having the following solids composition in parts by weight:

100 parts Gelva C5-V10 [(tradcmark of Shawinigan Resins Corp.) a poly(vinyl acetate-crotonic acid) copolymer] 5 parts ammonium hydroxide (20% NH 7.5 parts silica 2 parts Titanox FMA titanium dioxide The ammonium hydroxide is used to solubilize the Gelva resin, and flashes off when the coat is dried. The silica is used to provide a non glossy matte surface. The titanium dioxide is used to space the receiver sheet from the image bearing element during image transfer, as described in U.S. Pat. No. 3,519,819.

This aqueous dielectric coating formulation is coated over the dried conductive coat at 2.2 pounds per 1000 square feet of paper and allowed to dry. its surface resistivity is greater than 1 X ohms per square at 20 percent relative humidity with parallel bar electrodes at 500 volts, and it is not dissolvable in water.

The opposite side of the paper base may then be coated, if it has not already been done, with a conductive coating in the same way as described above and using the same conductive composition.

The finished receiver sheet is capable of accepting 420 volts charge on the dielectric coat and has a decay rate of only about 3 volts per second for the first sec onds after charging, which demonstrates its usefulness as a receiver sheet in a charge transfer system of electrography.

In order to demonstrate the improved conductivity secured by the present invention wherein the conductive coating is applied directly to a dense nonpenetrable paper base, and to demonstrate how closely its conductivity approaches that of the same coating applied on an absolutely dense non-absorptive and non-penetrable base, the same conductive coating of Example 1 is applied in the same thickness to a porous paper sheet, to a dense non absorptive non porous cellulose acetate butyrate sheet, and to the uncoated paper base sheet of Example 1 (without a dielectric coat), and the surface resistivity at percent relative humidity and 500 volts is measured:

Same formulation as in Example 1 except level of refining reduced to seconds Williams Slnwncss, and resultant Sheffield Porosity is 308 units corresponding to 35 seconds air resistance.

The above data indicate that the coated dense paper base of the invention is two orders of magnitude more conductive (less resistive) than the coated porous paper base, and is only slightly less conductive than the coated film of cellulose acetate butyrate.

Example 2 In order to demonstrate that an aqueous dielectric coating can be applied directly over a conductive coat with no significant loss of charge acceptance, compared to a paper wherein the aqueous dielectric coat is applied over a non conductive precoat layer, a paper base is prepared as in Example 1 except that instead of applying an aqueous dielectric coat over a dried aqueous conductive coat, the dielectric coat is applied over a precoat deposited from an aqueous dispersion di-' rectly on the paper and comprising a non conductive pigmented coating having the following formulation:

Ultra-cote (trademark of Englehard Minerals and Chemicals) No. 2

coating clay 100.0 dry parts Essex Gum 1390 30.0 dry parts Nopcote C-104 (trademark of Nopco Chemical Co.) 50% calcium stearutc 1.0 dry parts The opposite sides of both papers carry the same conductive coats described in Example 1.

Surface Resistivity Volume Resistivity (ohms/square) (ohm-cm l Example 1 110 X 10 4,) X 10" Example 2 1.0 X l0 l 2 X 10 After applying a dielectric coat on each sample, as in Example I, the paper of Example 2 is capable of accepting 375 volts and has a decay rate of about 3 volts per second for about the first 15 seconds after charging. The paper of Example 1 (the invention) accepts 380 volts and has the same decay rate. These results clearly show that detrimental migration of the conductive material into the dielectric material does not occur with the formulation and configuration of Example 1. whereas such migration has been experienced when making papers of the prior art.

It should be noted that the element of Example 2 exhibits such high volume resistivity of the precoat that it would give unacceptable electrophotographic results at low humidities such as 10-20 percent relative humidity, whereas the conductive coating of the invention provides excellent results over a wide range of humidities such as 12-65 percent.

It has been found that with the combination of the particular high density paper stock of my invention, and the particular thin conductive coating, similar resistivity (and conversely, conductivity) values have surprisingly been attained by use of approximately 84 percent less of the costly polymeric conductive material Dow ECR-34 than the prior art, thus greatly reducing the cost of the finished receiver sheet. This conclusion is based on the values in US. Pat. No. 3,110,621 wherein similar resistivity to the present invention required about 0.8 pound per 1,000 square feet, whereas in my invention only 0.12 pound per 1,000 square feet of the same conductive material is required for the same surface resistivity of 8 X 10 ohm per square measured at percent relative humidity.

Example 3 Example 1 is repeated, but instead of using Essex Gum 1,390 in the conductive coat, it is replaced by Pencote (trademark of Penick and Ford Ltd.) hydroxyethyl corn starch, and the conducting agent is distributed at 0.13 pound per 1,000 square feet. The surface resistivity of the conducting coat is 3.2 X 10 ohms per square at 20 percent relative humidity.

Examples 4, 5 and 6 Example 1 is repeated, but instead of using Gelva C5- V10 in the dielectric coat, it is replaced by other polymers to compare their charge acceptance relative to the low (50 volt) charge acceptance of prior art receiver sheets wherein the conductive polymer has migrated into the dielectric coating.

Example Polymer Charge acceptance 5 Goodrite 1800 X 73 (trademark of B. F. Goodrich Co.) (poly- -Continued 7 Dow 636 polystyrene-butadiene latex (Dow Chemical Co.) 450 volts In the foregoing description certain tests and components have been described in a general way. A more specific definition of each is as follows:

Conductive Agents: The Dow ECR-34 conducting agent is water soluble polyvinylbenzyltrimethylammonium chloride which is one of many water soluble conducting agents coming within the scope of US. Pat. No. 3,01 1,918, generally classified as polymerized vinyl benzyl quaternary ammonium compounds, either homopolymers or copoylmers of any two or more such compounds with one another. Reference is made to US. Pat. No. 3,011,918 for further descriptive detail of such compounds.

Other conductive agents such as carbon black, and such metal powders as aluminum and nickel can be used but tend to impart undesirable color-to the receiver sheets whereas the polymeric conductors do not. Such inorganic salts as sodium and potassium chloride can be used when the receiver sheet is to be used only at high humidity such as 50 percent or higher relative humidity, but at low humidity such as 10 percent they are not conductive enough.

Sheffield porosity is described in an article entitled, Paper Testers For Instantaneous Measurement Of Smoothness And Porosity by W. I. Wilt and N. E. Emmons published in TAPPI, Vol. 39, l, l/56.

Williams Slowness is described in Bulletin No. 3, entitled New Precision Model Williams Freeness, Beating And Consistency Tester published by Williams Apparatus Company Inc., Watertown, N. Y.

Surface Resistivity measurement is described in G. F. Nadeau et al, U.S. Pat. No. 2,801,191, issued July 30, 1957.

Volume Resistivity measurement is described in an article by Andrew Blanch, Science Eng. Series 102, thatappeared in Electro-Technology for June, 1967.

TAPPI is an abbreviation for Technical Association of the Pulp and Paper Industry.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A receiver sheet for electrostatic recording comprising a dense paper base sheet having a bulk porosity of less than 200 Sheffield units as measured by a Sheffield Porosimeter with a 1 /2 inch orifice and air at 1% pounds per square inch, said paper base sheet being substantially free of conductive material;

a thinly distributed first electrically conductive coat on one side of said paper base sheet, said coat being present in an amount between 0.05 and 0.25 pound per 1,000 square feet, and containing between about and by weight of an electrically conductive material which comprises a homopolymer or copolymer of a vinylbenzyl quaternary ammonium compound;

a dielectric coat over and in contact with said first electrically conductive coat, said dielectric coat comprising predominantly a dielectric synthetic resin, and having a surface resistivity greater than 1 X 10 ohms per square at 20 percent relative humidity, and being substantially free of electrically conductive material, and;

a second electrically conductive coat on the opposite side of said paper base.

2. A receiver sheet in accordance with claim I, wherein said first conductive coat also contains binder and solid pigment particles.

3. A receiver sheet in accordance with claim I, wherein said electrically conductive material is polyvi nylbenzyl trimethyl ammonium chloride.

4. A receiver sheet in accordance with claim I wherein said paper base sheet has a Sheffield porosity of or less Sheffield units.

5. Paper comprising a dense paper base sheet having a bulk porosity of less than 200 Sheffield units as measured by a Sheffield Porosimeter with a 1 /2 inch orifice and air at We pounds per square inch, said paper base being substantially free of conductive material;

a thin first electrically conductive coat on one side of said paper base sheet containing about 20 to 30 percent by weight of an electrically conductive material comprising a homopolymer or copolymer of a vinylbenzyl quaternary ammonium compound, said coat being so distributed as to provide said conductive material in a coat weight between about 0.001 and about 0.5 pound per 1,000 square feet of paper; and

a second electrically conductive coat on the opposite side of said paper base.

6. Paper in accordance with claim 5 wherein said electrically conductive material is polyvinylbenzyl trimethyl ammonium chloride.

7. A method for making electrographic paper comprising:

providing a dense paper base sheet having a porosity of less than 200 Sheffield units as measured by a Sheffield Porosimeter with a 1 /2 inch orifice and air at 1%. pounds per square inch;

applying on one side of said paper base sheet a first aqueous dispersion or solution containing on a dry basis between about 20 and 30 percent by weight of an electrically conductive material which comprises a homopolymer or copolymer of vinylbenzyl quaternary ammonium compound and so distributing said dispersion or solution as to provide a thin first electrically conductive coat containing said conductive material in an amount between about 0.05 and 0.25 pound per 1,000 square feet;

causing water to evaporate from said first aqueous dispersion or solution and leave a dry first conduc tive coat;

applying on said dry first conductive coat a second aqueous solution or dispersion comprising dielectric material comprising predominantly a dielectric synthetic resin;

allowing water to evaporate from said second aqueous solution or dispersion and leave a dry dielectric coat; and

applying a second coat of conductive material on the opposite side of said paper base sheet from said first side of said paper base sheet from said first conductive coat;

said first aqueous dispersion or solution being so thinly distributed over said paper that substantially first and second aqueous solutions or dispersions also contain binder and solid pigment particles.

9. A method in accordance with claim 7 wherein said electrically conductive material is polyvinylbenzyl trimethyl ammonium chloride. 

1. A receiver sheet for electrostatic recording comprising a dense paper base sheet having a bulk porosity of less than 200 Sheffield units as measured by a Sheffield Porosimeter with a 1 1/2 inch orifice and air at 1 1/2 pounds per square inch, said paper base sheet being substantially free of conductive material; a thinly distributed first electrically conductive coat on one side of said paper base sheet, said coat being present in an amount between 0.05 and 0.25 pound per 1,000 square feet, and containing between about 20 and 30% by weight of an electrically conductive material which comprises a homopolymer or copolymer of a vinylbenzyl quaternary ammonium compound; a dielectric coat over and in contact with said first electrically conductive coat, said dielectric coat comprising predominantly a dielectric synthetic resin, and having a surface resistivity greater than 1 X 1016 ohms per square at 20 percent relative humidity, and being substantially free of electrically conductive material, and; a second electrically conductive coat on the opposite side of said paper base.
 2. A receiver sheet in accordance with claim 1, wherein said first conductive coat also contains binder and solid pigment particles.
 3. A receiver sheet in accordance with claim 1, wherein said electrically conductive material is polyvinylbenzyl trimethyl ammonium chloride.
 4. A receiver sheet in accordance with claim 1 wherein said paper base sheet has a Sheffield porosity of 120 or less Sheffield units.
 6. Paper in accordance with claim 5 wherein said electrically conductive material is polyvinylbenzyl trimethyl ammonium chloride.
 7. A METHOD FOR MAKING ELECTROGRAPHIC PAPER COMPRISING: PROVIDING A DENSE PAPER BASE SHEET HAVING A POROSITY OF LESS THAN 200 SHEFFIELD UNITS AS MEASURED BY A SHEFFIELD POROSIMETER WITH A 1 1/2 INCH ORIFICE AND AIR AT 1 1/2 POUNDS PER SQUARE INCH; APPLYING ON ONE SIDE OF SAID PAPER BASE SHEET A FIRST AQUEOUS DISPERSION OR SOLUTION CONTAINING ON A DRY BASIS BETWEEN ABOUT 20 AND 30 PERCENT BY WEIGHT OF AN ELECTRICALLY CONDUCTIVE MATERIAL WHICH COMPRISES A HOMOPOLYMER OR COPOLYMER OR VINYLBENZYL QUATERNARY AMMONIUM COMPOUND AND SO DISTRIBUTING SAID DISPERSION OR SOLUTION AS TO PROVIDE A THIN FIRST ELECTRICALLY CONDUCTIVE COAT CONTAINING SAID CONDUCTIVE MATERIAL IN AN AMOUNT BETWEEN ABOUT 0.05 AND 0.25 POUND PER 1,000 SQUARE FEET; CAUSING WATER TO EVAPORATE FROM SAID FIRST AQUEOUS DISPERSION OR SOLUTION AND LEAVE A DRY FIRST CONDUCTIVE COAT; APPLYING ON SAID DRY FIRST CONDUCTIVE COAT A SECOND AQUEOUS SOLUTION OR DISPERSION COMPRISING DIELECTRIC MATERIAL COMPRISING PREDOMINANTLY A DIELECTRIC SYNTHETIC RESIN; ALLOWING WATER TO EVAPORATE FROM SAID SECOND AQUEOUS SOLUTION OR DISPERSION AND LEAVE A DRY DIELECTRIC COAT; AND APPLYING A SECOND COAT OF CONDUCTIVE MATERIAL ON THE OPPOSITE SIDE OF SAID PAPER BASE SHEET FROM SAID FIRST SIDE OF SAID PAPER BASE SHEET FROM SAID FIRST CONDUDCTIVE COAT; SAID FIRST AQUEOUS DISPERSION OR SOLUTION BEING SO THINLY DISTRIBUTED OVER SAID PAPER THAT SUBSTANTIALLY NONE MIGRATES INTO SAID SECOND AQUEOUS SOLUTION OR DISPERSION SO THAT THE DRY DIELECTRIC COAT REMAINS SUBSTANTIALLY FREE OF CONDUCTIVE MATERIAL AND EXHIBITS A SURFACE RESISTIVITY OF AT LEAST 1 X 10**16 OHMS PER SQUARE FEET AT 20% RELATIVE HUIMDITY.
 8. A method in accordance with claim 7 wherein said first and second aqueous solutions or dispersions also contain binder and solid pigment particles.
 9. A method in accordance with claim 7 wherein said electrically conductive material is polyvinylbenzyl trimethyl ammonium chloride. 